Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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833 FXUS65 KFGZ 201755 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 1055 AM MST Fri Sep 20 2024 .SYNOPSIS...A low pressure system will bring cooler temperatures, gusty winds, and chances for showers and thunderstorms tonight through Saturday. Warmer and drier weather is expected to return for much of the upcoming week. && .UPDATE...Partly cloudy skies are being observed across northern Arizona this morning in response to the approaching upper level low over southern California. The low will slowly approach Arizona today with another mild and breezy day in store. Most precipitation chances will hold off until after dark, with the exception of a few isolated showers or storms across far western Coconino/Yavapai counties. The forecast is in line with the latest high-resolution model guidance this morning and only minor updates were made to the cloud cover this morning. && .PREV DISCUSSION /533 AM MST/...An upper level low pressure system continues to spin across southern California early this morning. As we move through the day the low will start to track to the east to northeast and will cross through Arizona tonight through Saturday. Models continue to support precipitation, mainly along and north of a Prescott to Window Rock line. The low is not moving particularly fast as it is cut off in both the mid and upper levels. The slow movement of the low will mean the precipitation will linger into Saturday, likely ending during the afternoon. It is still looking like a meager event with most areas seeing less than 0.25" of rain. There is some instability available along with some shear so thunderstorms are possible as the low makes its way across the region. However, the best shear/instability is offset from the onset of the precipitation and while there may be a few stronger storms that develop, it is not looking like we will see much in the way of strong/severe storms and any that do develop will be fairly isolated. Additionally, there is the possibility that some snow may fall across the San Francisco peaks but with snow levels generally above 10,000 ft, any accumulation will be light. A couple more facets of this low will be the cooler temperatures across the region along with some gusty winds. Saturday will be the coolest of the the next couple of days with temperatures averaging 5-10 degrees below normal across the entire forecast area. The low moves off to the northeast by late Saturday and we see things starting to clear out as a ridge starts to build across the west. Temperatures will warm and conditions dry out once again heading into the new week. A couple of kinks in the forecast come in the shape of cut off lows and shortwave troughs. A trough looks to drop down from the north, crossing through the Four Corners area on Tuesday. This may bring a chance for some isolated showers and gusty winds. A second cut off low may also develop along the California coast but the strength and depth of the approaching Four Corners trough early in the week looks like it may keep this low off to our west before deflecting the low off to the north as the ridge builds over the southwest during the middle of the week. Lots of moving parts in this forecast with plenty to grab our attention over the coming days. && .AVIATION...Friday 20/18Z through Saturday 21/18Z...VFR conditions will prevail for most areas through 06Z. Expect south to southwest winds at 10-20 kts gusting to 20-30 kts through 01Z then diminishing. After 06Z, scattered -SHRA/-TSRA and MVFR conditions west of a KPRC-KPGA line after 06Z with chances gradually increasing and spreading eastward through 18Z. OUTLOOK...Saturday 21/18Z through Monday 23/18Z...Scattered -SHRA/-TSRA and MVFR conditions will continue during the day Saturday. Greatest chances will be along and east of a KPRC-KFLG- KPGA line. VFR conditions with clear skies return later Saturday night into Sunday. West-northwest winds at 10-20 kts on Saturday, then variable winds mostly 10 kts or less for Sunday and Monday. && .FIRE WEATHER...Today and Saturday...An area of low pressure approaching from the west will bring increasing chances for showers and thunderstorms today through Saturday. South winds 15-25 mph this afternoon, followed by west-northwest winds 10-20 mph Saturday. Sunday through Tuesday...Warmer and drier Sunday and Monday with afternoon humidity in the 10-20% range. Humidity increases slightly Tuesday with a 10-15% chance of rain. Light west to north winds under 15 mph are likely Sunday and Monday, with northerly winds 10- 20 mph Tuesday. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...MCT/Meola AVIATION...McCollum FIRE WEATHER...MAS For Northern Arizona weather information visit weather.gov/flagstaff